Unless retired, transferred to the Retired Reserve, or discharged at an earlier date, each reserveofficer of the Army, Air Force, or Marine Corps in the grade of brigadier general who has not been recommended for promotion to the grade of major general, and each reserve rear admiral (lower half) of the Navy who has not been recommended for promotion to the grade of rear admiral, except an officer covered by section 14512 of this title, shall be separated in accordance with section 14515 of this title on the last day of the month in which the officer becomes 62 years of age.